Mitt Romney announced that Paul Ryan will be his Republican running mate in the 2012 U.S. presidential election.

If elected as what Americans call the veep, Ryan will join a colourful list of office holders who’ve said and done some extraordinary things.

Many on the list didn’t think too highly of the vice-presidency. Harry Truman — the 34^th vice-president and later 33^rd president — once said, "Look at all the vice-presidents in history. Where are they? They were about as useful as a cow's fifth teat."

And John Nance Garner, Franklin Roosevelt’s second in command, said the vice-presidency was "not worth a warm bucket of spit."

While vice-presidents might not have made a great impact on U.S. governance, they have provided some memorable moments. Here are some interesting facts about the veeps.

What are the chances a vice-president will someday become president?

About one in three. That's based on the first 43 vice-presidents, since the men who held that office after George H. W. Bush moved into the oval office in 1989 could still become president.

Four vice-presidents inherited the office after the president died due to natural causes. These include:

• John Tyler, for William Henry Harrison in 1841.
• Millard Fillmore, for Zachary Taylor in 1850.
• Calvin Coolidge, for Warren Harding in 1923.
• Harry Truman, for Franklin Roosevelt in 1945.

Another four rose to the office after the president was assassinated. These include:

• Andrew Johnson, for Abraham Lincoln in 1865.
• Chester Arthur, for James Garfield in 1881.
• Theodore Roosevelt, for William McKinley in 1901.
• Lyndon Johnson, for John Kennedy in 1963.

How many were elected to the presidency after having previously served as vice-president?

Republican presidential candidate Mitt Romney, left, listens to his vice presidential running mate Rep. Paul Ryan, R-Wis., speak at a rally August 12, in Mooresville, N.C. at the NASCAR Technical Institute. (Jason E. Miczek/Associated Press)

Four won elections to the White House after serving as vice-president:

• John Adams succeeded George Washington in 1789.
• Thomas Jefferson succeeded Adams in 1801.
• Martin Van Buren succeeded Andrew Jackson in 1837.
• George H.W. Bush succeeded Ronald Reagan in 1989.

Former vice-president Richard Nixon later became president, but only eight years after he left the vice-presidency. Nixon was re-elected in 1972, only to become the first U.S. president to resign (after the Watergate scandal).

When Nixon resigned as president, his vice-president, Gerald Ford, moved into the oval office.

How many vice-presidents have resigned while in office?

There were two:

• John Calhoun served under John Quincy Adams and then Andrew Jackson, and resigned in 1832 over political differences with Jackson.
• Spiro Agnew, Richard Nixon's vice-president, resigned in 1973 after charges of tax evasion and bribe-taking surfaced. Gerald Ford replaced Agnew, and later Nixon as president, making Ford the only person to become an unelected president.

Which vice-presidents faced criminal charges?

After he resigned, Agnew pleaded no contest to the criminal charges he faced.

Aaron Burr was the only vice-president to be accused of murder. Elected in 1801, Burr challenged U.S. founding father Alexander Hamilton to a duel.

In their 1804 duel, Burr shot and killed Hamilton. Burr eventually returned to his office in Washington and served out his term.

He was charged for murder in New Jersey and New York, but was never brought to trial.

After leaving office, Burr faced charges of treason for the attempted secession of the Louisiana Territory, an area that’s a third of the U.S today. He was acquitted in 1807

John Breckinridge was declared a traitor by the U.S. Senate in 1861. Breckinridge had been VP from 1857-1861. In 1860 he ran for president, losing to Abraham Lincoln.

Breckinridge had already been appointed a Senator by the Kentucky legislature but after Kentucky backed the Union, Breckinridge joined the Confederate rebellion, leading to the treason declaration.

He became a general in the Confederate army and eventually their Secretary of War. With the defeat of the Confederacy, he fled the U.S., spending part of his exile in Niagara-on-the-Lake, Ont. He returned to the U.S. in 1869, following a general amnesty for ex-Confederates.

Who is the shortest-serving vice-president?

William King, the 13^th vice-president. Soon after the election, a tuberculosis cough worsened and he travelled to Havana, Cuba, in the hope that the warmer climate might ease his health. Too ill to take the oath unaided, in 1853 King became the only vice-president to assume office while outside America. After being vice-president for three weeks, he died in his hometown of Mobile, Alabama. King was also the only vice-president who was not married.

Who’s the youngest and who's the oldest?

The youngest was John Breckinridge, who began serving at the age of 36 under President James Buchanan in 1857 – just one year above the office’s age of eligibility.

The oldest U.S. vice-president was Alben Barkley, who became Harry Truman’s veep in 1949 at the age of 71.

Have there been any female vice-presidents?

No woman has been elected to the office yet but both Democrats and the Republicans have fielded a female candidate. Geraldine Ferraro ran with Democratic presidential candidate Walter Mondale in 1984, while Sarah Palin ran with Republican hopeful John McCain in 2008.

Have any dabbled in show business?

In his late 20s, Gerald Ford gave modelling a try. Ford appeared in Look Magazine and on the cover of Cosmopolitan.

Vice-president Alben Barkley also had an on-screen career. In 1951 he appeared on Man of the Week and later hosted the current affairs show Meet the Veep.

Which party has had more vice-presidents?

Al Gore is one of three U.S. vice-presidents who have won the Nobel Peace Prize. Gore introduces incumbent Vice-President Joe Biden to the crowd at the annual Tennessee Democratic Party Jackson Day on July 16, 2010 in Nashville, Tenn. Mark Humphrey/Associated Press

• Republicans have 20.
• Democrats have 18.
• The Democratic-Republican Party had six.
• The Whig Party had two.
• The Federalists had one (John Adams, the first VP and second U.S. president.)

Has any vice-president won the Nobel Peace Prize?

While some vice-presidents have become punchlines, others have made significant contributions to the world.

Three vice-presidents have received the Nobel Peace Prize.

• Theodore Roosevelt, VP 1901-1905, won in 1906, while president, for contributing to the end of the Russo-Japanese war.
• Charles Dawes, VP 1925-29, won in 1925 for his creation of the Dawes Plan, to rebuild the German economy after the First World War.
• Al Gore, VP 1993-2001, won in 2007, along with the Intergovernmental Panel on Climate Change for their work to raise awareness about global warming.